A NEW  FORM  OF  CATALYTIC  PLATINUM 


BY 

VANDERVEER  VOORHEES 

B.  S.  University  of  Illinois,  1921 


THESIS 

SUBMITTED  IN  PARTIAL  FULFILLMENT  OF  THE  REQUIREMENTS  FOR 
THE  DEGREE  OF  MASTER  OF  SCIENCE  IN  CHEMISTRY,  IN  THE 
GRADUATE  SCHOOL  OF  THE  UNIVERSITY  OF  ILLINOIS,  1922 


URBANA.  ILLINOIS 


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1 HEREBY  RECOMMEND  THAT  THE  THESIS  PREPARED  UNDER  MY 
SUPERVISION  BY_  Vanlerveer  Voorhees 

ENTITLED A New  Form  of  Catalytic  Plat inum 


BE  ACCEPTED  AS  FULFILLING  THIS  PART  OF  THE  REQUIREMENTS  FOR 
the  degree  OF Master  of  Science 


Recommendation  concurred  in* 


Committee 

on 

Final  Examination* 


•Required  for  doctor’s  degree  but  not  for  master’s 


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THEORETIC  A L 


The  Catalytic  Process. 


The  catalytic  activity  of  platinum  was  first  noticed  in 
1317  by  Edmund.  Davy  when  he  discovered  that  a platinum  wire  in- 
duced the  combustion  of  inflammable  vapors  (methyl  alcohol,  ether, 
etc.)  at  tempera turesA below  their  kindling  point.  Later  experi- 
ments showed  that  by  carefully  reheating  the  wire  in  air  a number 
of  times,  the  temperature  at  which  it  would  glow  spontaneously 
could  be  lowered  to  50°c.  A practical  use  and  scientific  curiosity 
resulting  from  the  above  discover;;  was  Davy's  glow  lamp,  a coil  of 
platinum  wire  suspended  above  a volatile,  inflammable  liquid. 

Shortly  after  this^Davy  prepared  platinum  in  a very  fine 
tate  of  division  by  digesting  the  nitrate  (?)  with  alcohol  and  ob- 
tained essentially  the  product  known  as  "platinum  black."  This  na- 
erial  was  a black  amorphous  powder  having  the  same  catalytic  pro- 
perties as  the  platinum  wire  but  to  a much  greater  extent.  It  would 
gnite  an  inflammable  vapor  at  ordinary  temperature  and  sometimes  ex- 
lode weakly  on  heating.  Since  this  time  numerous  modifications  have 
oeen  made  in  the  method  of  preparing  platinum  black,  many  uses  have 
peen  found  for  the  material  because  of  its  remarkable  catalytic  ac- 
lvity  and  many  theories  have  been  proposed  to  account  for  its  pecu- 
iar  properties,  but  today  after  more  than  a hundred  years  of  <jili- 
:ent  research,  chemists  are  still  disagreed  concerning  the  processes 
Uhich  give  platinum  its  catalytic  power. 


1)  Phil.  Mag.  (1820) 


330 


-2- 

Of  the  theories  advanced  for  the  behavior  of  platinum  black, 
the  two  of  greatest  importance  are  the  adsorption  theory  and  the  ox- 
ide theory.  The  former  assumes  that  in  the  case  of  oxidation,  oxygen 
condenses  or  is  adsorbed  onto  the  surface  of  the  platinum  in  which 
state  its  concentration  might  account  for  the  increased  chemical  ac- 
tivity. In  reduction  it  is  the  hydrogen  which  is  adsorbed,  perhaps 
as  a loose  chemical  combination  from  which  it  is  split  off  in  atomic 
form. ^ 1 2 ^ 

The  oxide  theory  assumes  the  absorption  of  oxygen  in  oxida- 
tions to  be  due  to  the  formation  of  an  oxide  of  platinum  which  is 
then  capable  of  acting  as  an  oxidizing  agent.  Similarly,  reduction 
is  the  formation  of  metallic  platinum  which  has  a great  affinity  for 
oxygen  and  hence  can  act  as  a reducing  agent.  The  mechanism  of  this 
process  differs  with  different  authors.  Wohler  assumed  the  formation 
of  hydrogen  peroxide  as  follows: 

H 0 H 0 OH 

Pt  + f " --->  Pt'  H 0 0 H 

H 0 H 0 v0  H 

Tillstatter^ c has  assumed  the  formation  of  an  oxyperoxide  of  plati- 
num in  oxidation: 

> 0 0 0 H 

Pt  + °2  pt  ’ Pt  Oo  + HoO  --->  Pt 

«---  x 0 V0  H 

and  a hydro  platinic  acid  in  reduction: 

0 H\  / 0 

Pt  ^ ' + H2  --->  Pt  ' 

^ 0 W No 


(1)  C.  C.  (1835)  458  Ber.  41,  1984,  1998  (1911) 

(2)  Ber.  (1921)  113 


' 


: 


-3- 


The  adsorption  theory  has  many  weaknesses.  It  does  not 
readily  explain  the  reduction  of  H N 03*  K Cl  0^  etc.  by  dextrose  in 
the  absence  of  hydrogen  gas  . ^ ; It  encounters  great  difficulty  in 
explaining  the  lack  of  catalytic  activity  of  platinum  in  hydrogen  when 
entirely  freed  from  oxygen. ^ Careful  experiments  by  Mond,  Ramsay 
and  Shields  showed  that  platinum  black  contained  oxygen,  the  bulk 
of  which  is  not  liberated  until  the  temperature  is  raised  to  400°. 

Also,  the  platinum  black  would  absorb  300  volumes  of  hydrogen,  200 
volumes  combined  with  the  oxygen  present,  and  the  heat  of  absorption 
corresponded  with  the  heat  of  formation  of  the  water  produced,  and 
that  the  remainder  could  be  removed  at  250°.  An  increase  of  pressure 
from  1 to  4 atmospheres  has  almost  no  effect  on  the  quantity  of  either 
hydrogen  or  oxygen  absorbed.  Platinum  charged  with  oxygen  absorbs 
still  more  on  heating  to  360° , whereas  platinum  charged  with  hydrogen 
and  heated  to  360°  loses  the  dissolved  gas. 

From  the  above  data,  the  postulation  of  hydrides  of  platinum 
as  the  active  catalytist  in  reduction  seems  quite  unsupported. 

The  oxide  theory  has  been  assailed  by  the  adsorpt ionlsts  as 
ansound  on  the  ground  that  oxides  of  platinum  do  not  exist.  The 
jreat  resistance  of  platinum  to  oxidation  is  attested  by  its  use  in 
analytical  crucibles  etc.  where  the  slightest  oxidation  would  be  fatal 
-o  accuracy.  However,  that  oxides  of  platinum  do  exist  has  been  dem- 
onstrated conclusively  by  numerous  investigators.  Following  are  refer, 
onces  to  the  results  of  some  of  them: 


(1)  Bull.  Coll.  Agr . Tokyo  Imp.  Univ.  7,  1-6  (1906) 

(2)  Ber.  (1921)  113 

(3)  Proc.  Roy.  Soc . 58,  242  (1895) 


-4-  “ ' “ — — — ' ‘ 

Topstte^'  ^determined  the  composition  and  properties  of  Pt  0.- 
prepared  in  the  manner  of  Doebereiner,  Wittstein  and  Fremy.  Na  Pt 
Clg  is  treated  with  excess  Na  0 H and  on  acidification  with  acetic 
acid  a hydrated  Pt  Og  is  precipitated.  Pt  Og’4  HgO  loses  2 HgO  at 
100°  Frost ^ ^dissolved  the  above  hydrate  in  H N 0„  and  on  dilution 
obtained  Pt  Og * 3 PlgO. 

.Ln  1877  Thomsen^ ^obtained  Pt  0 by  boiling  potassium  chloro- 
platinite  (Kg  Pt  Cl^)  with  alkali.  It  is  a strong  oxidizing  agent, 
converting  formic  acid  to  C Og . In  the  same  year,  Jorgensen^1 2 3  4 5 6 ^ pre- 
pared what  he  called  "plat inoxydul  oxide"  by  a sodium  carbonate  fusioi 
of  Nag  Pt  Clg.  It  is  a bluish  black  powder,  stable  to  aqua  regia  and 
heat,  and  is  reduced  by  hydrogen  and  by  formic  acid  in  the  cold,  the 
latter  yielding  C 0 . Analysis  showed  a composition,  Pt-  0/. 

By  heating  platinum  sponge  with  Nag  0^f}a  rapid  oxidation  of 
the  platinum  takes  place,  Ptg  0,  being  produced.  It  is  a yellow  pow- 
der when  hydrated  but  on  heating  to  450°  a dark  brown  powder  results 
'Thich  is  only  slowly  attacked  by  aqua  regia.  By  electrolysis  of  fused 
sodium  or  potassium  nitrates  between  electrodes  of  platinum  foil, 
iittorf  obtained  yellowish  brown  and  green  oxides  of  platinum. 

Electrolysis  of  an  alkaline  solution  of  Pt  Og  between  plati- 
ium  electrodes  produces  a reddish  brown  powder  at  the  anode  which  has 


(1)  Ber.  3,  462  (1870) 

(2)  Ber.  19  Ref.  666  (1868) 

(3)  J.  Prakt.  Chem.  (2)  15,  284  (1877) 

(4)  J.  Prakt.  Chem.  (2)  16,  344  (1877) 

(5)  Am.  Chem.  J.  28,  59  (1902) 

(6)  (J.  C.  (1848)  23 


^5  = 

the  formula,  Pt  0.t  . ^ 1 ^ It  is  not  reduced  by  HgOg  but  dissolves  in 
dilute  H Cl  with  evolution  of  chlorine.  It  loses  oxygen  readily, 
forming  Pt  02  on  heating. 

In  his  classic  paper  on  platinum'  '7T6hler  has  shown  that  pla- 
tinum black  has  the  property  of  oxidizing  K I to  iodine  as  indicated 
by  the  starch  test.  From  its  partial  solulility  in  H Cl,  he  has  cal- 
culated it  to  contain  10-18%  Pt  0.  By  an  oxidation  in  oxygen  gas  at 
450°  Wtthler  obtained  44%  of  platinum  sponge  converted  to  platinum  ox- 
ide. Since  platinum  black  behaves  very  similarly  to  Pt  0,  Wfthler  as- 

|! 

signs  its  catalytic  properties  to  this  substance. 

Wi 11s  tatter  <3>has  now  shown  that  platinum  black  used  in  cata-l 
lytic  reductions  is  ineffective  when  deprived  of  its  oxygen,  and  that 
catalysis  is  resumed  after  the  catalyst  is  exposed  to  air  or  oxygen 
gas.  Much  work  has  been  done  on  the  poisoning  of  platinum  catalyst' 
and  it  is  seen  that  most  "poisons"  are  reducing  agents.  Platinum 

( 5 

poisoned  with  H C N may  be  revivified  by  a current  of  air  or  oxygen. 
The  necessity  for  oxygen  is  hard  to  explain  on  any  other  assumption 
than  that  an  oxide  of  platinum  is  the  active  catalyst. 

The  stability  of  some  of  the  platinum  oxides  is  quite  re- 
markable. Pt  0 does  not  decompose  appreciably  below  400°.  Pto  0S 
and  Pt^  04  are  stable  at  higher  temperatures  than  this  altho  Pt  0g 

loses  half  its  oxygen  at  280°.  Pt  Cf  reverts  to  Pt  Og  on  gentle  warm- 

o 


(1) 

Ber. 

42,  3326  (1909) 

(2) 

Ber . 

36,  3475  (1903) 

(3) 

Ber. 

(1921)  113 

(4) 

Zeit 

. Physikal.  Chern.  37,  1-68  (1901) 

(5) 

Zei  t 

. Physikal.  Chem.  37,  551  (1901) 

, 


“ 

■ 


-6- 


ing  altho  my  experiments  show  that  an  oxide  higher  than  Pt  Og  is 
quite  stable  at  somewhat  elevated  temperatures.  Pt3  04  retains  half 
its  oxygen  until  a temperature  approaching  1000°  is  reached. 

The  volatilization  of  platinum  in  electric  furnaces  at  com- 
paratively low  temperatures  followed  by  crystallization  on  the  cooler 
portions  of  the  furnace,  has  been  explained  by  Roberts ^ 1 2 3 ^by  the  form- 

•2V 

ation  of  Volatile  oxide  at  the  higher  temperature  which  is  unstable 
at  the  lower  one.  This  theory  is  supported  by  the  fact  that  volatil- 
ization does  not  take  place  in  an  atmosphere  of  hydrogen,  nitrogen  02 

in  a vacuum.  Furthermore  a similar  phenomenon  occurs  with  the  chlor- 

(o)  (3) 

ides'  ' and  with  the  fluorides. 


(1)  Phil.  Mag.  25,  270  (1913) 

(2)  Compt.  Rend.  947  (1877) 

(3)  Compt.  Rend.  807  (1889) 


=3= 


Preparation  and  Uses  of  Platinum  Black. *- 

Many  methods  have  been  given  for  the  preparation  of  platinum 
black,  each  claiming  an  advantage  over  those  previously  employed. 
However,  almost  all  of  them  have  this  in  common,  the  precipitation 
of  the  platinum  from  a solution  of  Pt  CI4  by  a reducing  agent  in  the 
presence  of  an  alkali. 

The  first  laboratory  method  for  making  platinum  black  was 

originated  by  Liebig^'^in  1829.  He  boiled  Pt  Clg  with  Kg  0 0^  and 

alcohol,  which  is  essentially  the  same  as  the  preparation  of  Pt  0 

as  given  by  Thomsen.^"  ^ In  1854  Doebereiner ' ' '^reduced  Pt  Cl^  with 

( 4 ) 

sugar  or  alcohol  in  a sodium  carbonate  solution.  Later,  Hempel  ' 

( 5 ) 

and  also  Brunner  reduced  Pt  Cl  in  alkali  by  means  of  ferrous  salts 

( 5 ) 

Fond,  Ramsay  and  Shields  v 'precipitated  platinum  black  from  Pt  Cl^ 

by  sodium  formate  in  sodium  carbonate.  Very  active  platinum  black 

(7) 

can  be  produced  by  boiling  Pt  Cl^  with  Rochelle  salt  and  with  gly- 

( 8 ) 

cerol  and  K 0 H.  It  has  also  been  made  by  passing  hydrogen  over 


*2 


Pt  Cl^  at  250°^“^  and  by  reduction  of  Pt  Cl,  with  aluminum  foil.^0 


•?:-  Footnote--In  German  literature  platinum  black  is  termed  " Platin- 
mohr"  from  the  word  Mohr  meaning  Moor  or  black. 

(1)  Pogc.  Ann.  17,  102  (1829) 

(2)  J.  Prakt.  Cbem.  (2)  15,  294  (1877) 

(3)  Ann.  2,  1 (1834) 

(4)  Ann.  107,  97  (1857) 

(5)  Ann.  109,  253 

(G)  Trans.  Roy.  Soc.  660  (1895) 

(7)  C.  C.  (1877)  576 

(8)  Bull.  Soc.  Chim.  25,  198  (1876) 


-8- 


The  most  widely  used  method  at  present  is  that  of  Loew^in 


which  he  reduced  Pt  Cl  with  formaldehyde  in  the  presence  of  sodium 
hydroxide.  The  reduction  is  incomplete  and  the  platinum  black  is 
semicolloidal  until  it  is  exposed  to  air  on  the  filter.  Air  is  ab- 
sorbed accompanied  by  a rise  of  temperature  and  loss  of  colloidal  na 
ture . Two  recent  methods  are  modifications  of  this  last,  the  object 

being  to  facilitate  the  preparation  by  avoiding  the  colloidal  form 

( 2 ) 

which  makes  washing  and  filtering  difficult.  Feulgen  'shakes  the 
precipitate  with  acetic  acid  when  it  tends  to  become  colloidal.  Aftejb 
thoro  washing  by  decantation  the  black  is  dried  in  a vacuum  and  on 
exposure  to  air  it  absorbs  oxygen  so  rapidly  that  it  glows  with  the 
heat  of  reaction,  Willst&tter ^ ^conducts  the  reduction  at  low  tem- 
perature and  employs  K 0 H vhLch  gives  the  crystalline  and  relatively 
coarse  Pt  Clg,  thus  bringing  down  the  platinum  black  in  particles 
which  permit  ready  decantation. 

Platinum  black  is  finding  considerable  use  in  the  catalytic 
reduction  of  organic  compounds  and  has  been  used  in  inorganic  reduc- 
tions and  oxidations  for  some  time;  N has  been  oxidized  by  air  to 
(4) 

N H4  N Og  and  S Og  to  S 0^  in  the  "contact  process."  Nitrogen  has 

„ (5)_  _ „ _ „ TT  (S')  , „ 


-9- 


Vavon^1 2 Ogives  a good  review  of  the  organic  reductions  hy  platinum 
black.  Acetaldehyde,  isoamylaldehyde  and  heptaldehyde  yield  the  cor- 
responding alcohols  while  acetone,  ethyl  methyl  ketone  and  diphenyl 
ketone  were  reduced  to  the  secondary  alcohols . 

Palladium  black  is  generally  conceded  to  be  a more  active  cata 
lyst  than  platinum  black  and  my  own  experiments  have  borne  this  out. 


However,  its  action  is  peculiarly  different  from  that  of  platinum. 

While  platinum  reduces  benzene  to  the  hexahydro  benzene,  palladium 

( 2 ) 

reduces  it  only  to  the  tetrahydro  derivative.  In  my  experiments 

I reduced  salicylaldehyde  rapidly  with  palladium  black  to  ortho  cre- 
sol,  a product  which  was  never  obtained  in  the  use  of  platinum  black 
under  widely  varying  conditions. 


(1)  Ann.  Chim.  Ser.  9,  1,  144 

(2)  Zeit.  Anorg.  Chem.  191  (1900) 


, 

■ 


, 


. 


-10- 


Exper  imental 

Assuming  that  the  catalytic  property  of  platinum  black  is  due 
to  an  oxide,  of  which  it  contains  only  18-20^,  it  would  appear  that 
the  pure  oxides  of  platinum  themselves,  particularly  the  higher  ox- 
ides, would  be  far  more  active  catalysts  than  platinum  black  as  usu- 
ally prepared.  Accordingly  an  oxide  of  platinum  was  prepared  in  the 
following  manner: 

1 gm.  of  platinum  was  dissolved  in  aqua  regia  and  the  result- 
ing solution  was  mixed  with  10  gm.  Na  N O3 . The  mixture  was  rapidly 
evaporated  to  dryness  and  fused  over  a Bunsen  flame  in  a small  porce 
lain  casserole  or  Pyrex  beaker.  Between  300°  and  400°,  red  oxides 
of  nitrogen  are  given  off  and  the  platinum  is  precipitated  as  a f^ne 
powder  ranging  in  color  from  a light  yellowish  brown  to  a dark  red- 
brown.  When  the  evolution  of  oxides  of  nitrogen  has  ceased,  the  fu- 
sion is  poured  into  a cool  casserole  and  allowed  to  solidify.  When 
cold,  it  is  dissolved  in  water  and  decanted  twice  from  the  oxide  thru 
a filter.  The  oxide  is  then  transferred  to  the  filter  and  washed 
several  times  until  free  from  nitrates.  The  powder  may  be  used  dir- 
ectly or  dried  and  used  at  intervals  . 

All  filtrates  should  be  tested  for  platinum  by  the  method  of 
Wtthler^^.  To  an  acidified  portion  is  added  a few  drops  Sn  Cl,-,  sol. 

A yellow  or  brown  color  indicates  platinum,  the  intensity  varying  witfli 
the  quantity.  The  color  may  be  shaken  out  with  ether  or  ethyl  acetat 
thus  giving  a very  sensitive  test.  The  filtrates  containing  platinum 

(1)  Chem.  Zeit.  31,  938  (1907^ 


• ■ 


. 


' 

. 

, 


. 


. 


-11- 


should  be  evaporated  and  re-fused  with  a little  sodium  carbonate 
which  will  throw  cut  the  platinum  quantitatively  as  a black  powder. 

Altho  this  method  has  not  been  found  in  the  literature,  Jor- 
gensen and  Dudley ( ^both  obtained  platinum  oxides  by  fusion  methods , 
and  it  was  thought  that  fusion  with  a strong  oxidizing  agent  like 
Na  N Og  would  produce  a higher  oxide . If  a mixture  of  h N 05  and 
Na  N O3  is  used  in  place  of  Na  N 03,  the  fusion  point  is  much  lower, 
but  the  oxide  seems  to  be  in  a less  finely  divided  form,  since  the 
crystalline,  insoluble  potassium  chloroplat inate  is  first  formed. 
Consequently  the  resulting  catalyst  is  less  active. 

Preparation  of  the  catalyst  at  different  temperatures . 

2-g  gram  samples  of  platinum  were  dissolved  In  aq . reg . and 
placed  in  50  CC  porcelain  crucibles  with  10  grams  of  Fa  N each. 
These  were  heated  carefully  in  an  electric  resistance  furnace,  the 
temperature  being  controlled  by  an  outside  resistance  and  the  fusion 
being  constantly  stirred  by  a thermocouple  encased  in  a Pyrex  tube 


Sample 

I 

Time 

Temperature 

Remarks 

0 min . 

— 

Placed  in  furnace 

4 " 

295° 

Pus  ion 

5 " 

305° 

Evolution  of  N O2  begun 

25  " 

385° 

Decomposition  almost  Complete 

35  " 

415° 

Evolution  of  N 0q  ceased 

40  " 

382° 

Removed  from  furnace 

(1)  loc . cit. 

(*-)  Temperature  readings  were  made  by  Mr.  T.  0.  Yntema. 


. 


-12- 


Sample  II 


Time 

Temperature 

Remarks 

0 

min . 

— 

Placed  in  furnace 

9 

it 

280° 

Fusion 

13 

tt 

320° 

Evolution  of  N o^  begun 

20 

tt 

415° 

Rapid  evolution  of  N Og . Exotherm! 

26 

11 

465° 

Decomposition  almost  complete 

32 

tt 

555° 

Odor  of  N Og  still  noticeable 

48 

tt 

504° 

Removed  from  furnace 

Sample 

III 

Time 

Temperature 

Remarks 

0 

min . 

— 

Placed  in  furnace 

5 

it 

290° 

Fusion 

10 

rt 

425° 

Rapid  decomposition 

23 

rt 

580° 

Evolution  of  N Og  praotically  osase 

29 

ii 

655° 

41 

it 

680° 

Still  faint  odor  of  N 0^ 

48 

tt 

— 

Removed  from  furnace 

After  cooling  the 

melts  were  extracted  with  water,  filtered 

and 

washed  free  from  nitrates . The 

filtrate  from  No.  I showed  a con- 

s iderable  quantity  of  platinum  in  solution,  but  No.  II  and  No.  Ill 
filtrates  contained  only  a trace. 

After  drying  in  a dessicator  over  H2  S 04  the  three  samples 
were  tested  for  catalytic  activity  by  the  reduction  of  salicyl  alde- 
hyde under  similar  conditions  as  follows: 

.5  gram  of  the  catalyst  was  placed  in  a 400  C.C.  bottle  with 
30  gm.  salicyl  aldehyde  and  100  C.C.  alcohol.  The  air  was  exhausted 
from  the  bottle  and  hydrogen  was  admitted  from  an  8 liter  tank  equippe  i 


-13- 


with  a pressure  gauge.  The  amount  of  hydrogen  absorbed  can  be  close- 
ly calculated  from  the  fall  in  pressure.  A drop  of  21.3  pounds  is 
equivalent  to  1 gm.  Hydrogen,  and  variation  of  pressure  with  room  tern 
perature  was  corrected  for.  The  bottle  was  suspended  in  a stirrup 
and  oscillated  by  a motor-driven  crank  which  produced  a constant  and 
violent  agitation  of  the  contents.  After  reduction,  the  alcoholic 
solution  of  saligenin  was  separated  from  the  catalyst,  the  alcohol 
distilled  off  under  diminished  pressure  and.  the  saligenin  crystallize 
from  benzene  in  shining  white  plates.  No  attempt  was  made  to  obtain 
the  exact  yield,  the  approximate  yield  being  merely  a rough  check  on 
the  experiment. 


Sample  I 

Olive  drab  amorphous  powder. 


Pressure 

Time 

30.0 

lbs . 

0 : 00  hr 

24.9 

0:11 

22.0 

0:22 

20.7 

0:58 

20.6 

1:30 

20.6 

2:20 

9.4 

- Total 

abs  orpti 

Remarks 


Catalyst  black  and  bottle  quite  warm 


(Theory  - 10.2) 


Catalyst  could  not  be  separated  by  decantation  but  filtered 
readily.  Yield  - 22  gm!.  saligenin. 


. 


- 


-14- 


3 ample  II 

Slightly  lighter  in  color  than  I 


Pressure 

Time 

Remarks 

29.9  lbs. 

0:00 

28.1 

0:50 

Catalyst  in  s emi colloidal  state. 
Olive  screen  color. 

25.2 

0:40 

25.0 

0:50 

Bottle  warm  from  heat  of  reaction 

21.5 

1:00 

19.8 

2:17 

Catalyst  a jet  black 

10.12 

- total  absorption 

Catalyst  was  difficult  to  separate  and  had  a tendency  to 
pass  through  the  filter. 

Yield  - 20  gm.  saligenin. 

Sample  III 

Slightly  lighter  color  than  II 


Pressure 

Time 

Remarks 

29.7  lbs  . 

0:00 

29.3 

0:26 

ro 

~o 

CD 

0:41 

26.2 

0:53 

Catalyst  an  olive  green  color 

21.8 

1:53 

20.5 

2:33 

19  .5 

3:43 

Catalyst  a greenish  black 

i 

CVJ 

• 

o 
1 — 1 

total  absorption 

Catalyst  did  not  settle  on  standing  over  night.  On  shaking 
with  a few  drops  of  acetic  acid  it  settled  completely  in  two  hours. 

Yield  of  saligenin  - 18  gm.  (some  loss  due  to  oxidation  in 
handling ) . 


■ . . 


, 


Ahsorpffn  Hy*(rofc~n  /n 


A +*mf 


-15- 


30  grams  more  salicylaldehyde  was  added  to  the  above  catalyst 
and  a second  reduction  made  to  show  whether  or  not  its  slow  action 
was  due  to  lag  at  start. 


Pressure 

Time 

30.1 

0:00 

29.2 

0:18 

28.9 

0:30 

27  .5 

0:51 

27  .2 

1:56 

23.3 

7:11 

20.1 

12:26 

10.0 

Yield  - 16  gm.  sa'ligenin. 

Analyses  of  foregoing  oxides . 

After  standing  in  a dedicator  over  sulfuric  acid  for  2-gj 
months,  the  oxides  were  analysed  by  heating  in  porcelain  crucibles 
at  varying  temperatures  in  an  electric  furnace  and  finally  over  a 
Meeker  burner  in  an  atmosphere  of  hydrogen  (Rose  crucible)  to  obtain 
complete  reduction  to  platinum.  Each  weighing  was  made  after  cooling 
the  crucible  in  a dessicator  in  which  a vacuum  of  1 m.m.  was  obtainec 
\ minute  after  the  crucible  was  removed  from  the  heat. 


Sample 

12  hrs . at  120° 

Loss  of  wt . on  heating: 
2 hrs . at  120° 

2 hrs . at  240° 

2 hrs  . at  360° 

(No  change  in  color) 


I II  III 

1.9528  2.5708  

2.3883 

.0104  .0220  

.0323  .0854  

.0073  .0164  


-Ie>-  ““ 

2 hrs.  at  700°  -----  .2410  

(dark  gray) 

20.  min.  with  Hydrogen  .2525  .4312 

II  III 

Percentage  loss  after  heating  at  120u  18.9  18.5 

Sample  II  was  heated  in  oxygen  over  a Meeker  burner  to  con- 
stant weight  and  found  to  absorb  5.21%  of  its  weight  of  oxygen  and 
become  dark  in  color.  Since  Pt  0 contains  8.16$  of  the  wt . of  pla- 
tinum as  oxygen,  the  above  absorption  corresponds  to  a conversion  of 
40$  of  the  platinum  sponge  to  Pt  0,  a value  very  near  that  obtained  bj 
WBhler  from  solubility  in  H Cl.'1 1/1 

Platinum  oxides  prepared  from  various  fusion  mixtures  and  their 
catalytic  activity. 

Various  mixtures  were  prepared  and  fused  rapidly  in  porcelair 
over  a Bunsen  burner,  the  temperature  being  gradually  raised  to  450° 
within  5 minutes.  The  melt  was  stirred  constantly  with  a pyrometer 
couple  enclosed  in  a pyrex  tube.* * 


Compositions  of  mixtures: 


I 

1 

gm. 

Pt  (as  Pt  Cl4) 

t 

10 

gm. 

Ha  N 0 

kJ 

II 

1 

gm. 

20 

gm. 

It 

III 

1 

gm . 

it 

+ 

10 

gm. 

IT 

f 

2 

gm.  Nag  C 0^ 

IV 

1 

gm. 

u 

10 

gm. 

" ♦ 

.2 

gm . Carbon 

(1)  Loc . cit. 

* Temperatures  read  by  Mr.  T.  0.  Yntema 


-17- 


The  object  of  the  carbon  was  to  reduce  some  Na  N 0^  to 
Na9  C O3  after  fusion  which  would  cause  complete  precipitation  of 
the  platinum. 

Samples  I and  II  were  incompletely  precipitated. 

Samples  III  and  IV  were  almost  entirely  precipitated. 

Samples  I and  II  were  a medium  brown  in  color. 

Samples  III  and  IV  were  a light  brown  and  yellow. 

The  catalysts  were  tested  as  follows:  30  gm.  salieylaldehyd 

f 60  C.C.  alcohol  were  shaken  with  .25  gm.  of  each  catalyst.  Result  1 


as  follows: 

Pressure 

Time 

Remarks 

Sample 

I 

30.8 

lbs  . 

0:00 

28.8 

0:11 

23.8 

0:33 

Bottle 

warm  and  catalyst  black 

21.9 

1:03 

21.1 

1:48 

Sample 

20.8 

10.0 

II 

2:02 

29  .6 

lbs  . 

0:00 

26  .2 

0:15 

Bottle 

warm 

23  .2 

0:30 

21.0 

0:55 

Sample 

20.1 
9 .5 
IV 

2:40 

30.2 

lbs  . 

0:00 

28.1 

0:21 

Bottle 

warm 

26.4 

0:31 

22.8 

1:31 

. 


■ 


/7  * 


I±t 

TF 

rF 

t± 

T+ 

5 

rq~ 

i 'i  i"j 

,1~~T~ 

hR-'-r 

±14- 

n '■  +-p 

r- - 

s 

- 

9 Cf  ^ £>  S Cf  \/  U ^ £ O -/  )* /• +-/  J.O 


f 


|l> 


\t 


7~ ? rri  e / r\  W / ft  h T e ? 


-18- 


Pressure 


Time 


Remarks 


Sample  IV  (cont.) 


20.9 


2:47 


20.9 


5:17 


Qualitative  Tests  on  Brown  Oxide  of  Platinum  prepared  by  Na  N 0? 

Fusion. 

1.  The  oxide  is  only  partially  soluble  in  boiling  dilute  H Cl.  In- 
soluble portion  dissolves  easily  in  H Br  with  evolution  of  Br^ . 

2.  It  is  incompletely  soluble  in  boiling  cone.  H Cl  or  aqua  regia. 

3.  It  dissolves  easily  in  dilute  H Cl  on  warming  with  SOg  to  give 

the  yellow  chlorplat inic  acid. 

4.  It  is  only  very  slightly  soluble  in  10$  Na  0 H. 

5.  It  is  quite  insoluble  in  boiling  concentrated  h w Cb  . 

6.  It  dissolves  easily  in  constant  boiling  H Br  with  liberation  of 
bromine  (detected  by  odor  and  by  shaking  out  with  chloroform) . 
Bromine  vapor  may  be  distilled  into  K I sol.  liberating  free  I0 . 
The  platinum  goes  into  solution  as  Hg  Pt  Brg  and  can  be  precipi- 
tated as  the  red,  slightly  soluble  potassium  salt. 

7.  The  oxide  does  not  change  color  on  treatment  with  EgOg  (3$) 
either  by  long  standing  in  the  cold  or  on  boiling.  It  catalyses 
the  liberation  of  oxygen,  however,  both  cold  and  hot. 

8.  On  boiling  with  alcohol  In  an  atmosphere  of  C Og  it  is  reduced 
to  a black  powder  in  3 minutes . The  odor  of  acetaldehyde  is 
detected . 

9.  When  damp  with  alcohol  and  exposed  to  air  the  oxide  will  ignite 
the  alcohol.  It  will  also  ignite  a mixture  of  hydrogen  and  air. 


* 


, 


. 


* 


, 


* 


-19- 

A Comparison  of  the  Catalytic  Activity  of  Platinum  Oxide  Prepared  by 
Sodium  Nitrate  Fusion  and  Platinum  Black  Prepared  by  Formaldehyde  Re- 

duction . 


.5  gm.  of  platinum  was  converted  to  the  oxide  by  a Na  11  0^ 
fusion  and  shaken  with  20  gm.  vanillin  + 100  C.  C.  alcohol.  Using  the 
same  catalyst,  the  reduction  was  repeated  four  times  to  test  the  wear- 
ing quality  of  the  catalyst.  Each  time  the  product  (Vanillyl  alcohol] 
was  decanted  from  the  platinum,  the  alcohol  evaporated  under  dim in. 
press,  and  the  vanillyl  alcohol  crystallized  from  hot  'water. 


Pressure 

Time 

First  run: 

23.1 

lbs  . 

9:00 

IS.  6 

0:20 

18.3 

0:35 

Yield  - 16.5  gm. 

17 .6 

0:50 

It . P . 116°  (uncorrected) 

17 .0 

1:55 

(Lit.  - 115°) 

17.0 

2:55 

16.8 

18 : 00 

Total 

absorpt ion -6 . 3 

lbs  . 

( Theory  5 . 

Second  run: 

25.2 

lbs  . 

0:00 

23.9 

0:20 

Yield  - IB. 5 gm. 

22.0 

1:00 

11. P.  116°  (uncorrected) 

21.2 

1:20 

19.4 

3:25 

Total 

absorption-5 .8 

lbs  . 

I 


ft 


N* 


'V 

to 


=^55= 

Pressure 

Time 

Third  run : 

25.9  lbs. 

0:00 

Yield  - 18.5  gm. 

22.0 

0 : 45 

M.P.  - 116. 5C  (uncorrected) 

20.7 

1 : 50 

20.5 

4:10 

5.4 

Fourth  run: 

25.4  lbs. 

0:00 

Yield  - 15.5  gm. 

23.3 

0:20 

M.P.  - 116°  (uncorrected) 

18.7 

1:40 

(Probably  some  leakage) 

18.0 

3 : 30 

7.4 

Platinum  black  was  prepared  according  to  the  directions  of 

Willstatter ^ 1 ' as  follows : 

.5  gm.  Platinum  as  Pt  CI4  was  dissolved  in  2 C .0 . water  to 
which  a few  drops  of  H Cl  was  added.  3.8  C ,C  . formaldehyde  (33;1)  was 
added  and  the  solution  cooled  in  ice  and  salt.  10.5  gm.  50p  K 0 H 
was  stirred  in  drop  by  drop  and  a yellow  paste  formed  which  gradually 
darkened  to  a black  mush.  The  mixture  was  warmed  to  GO0  for  -|-  hr. 
and  the  platinum  settled  out  as  a flocculent  precipitate.  Ibis  vas 
washed  by  decantation  four  times  with  100  C .C . distilled  water  and 
the  platinum  black  washed  free  from  water  by  alcohol.  Still  wet  with 
alcohol  it  vas  placed  in  the  reduction  bottle  with  20  gm.  Vanillin  t 
100  CC  alcohol. 


(1)  Ber.  113  (1921) 


l- 


Pr  e s s ur  e T irne 


. 8 lbs . 0:00  hr  . 


25 .2 
24.8 
24.4 
24.1 


1:45 

3:00 

6:15 

18:45 


.4  gm.  platinum  oxide  prepared  by  Na  N 0-  fusion 
now  added 


23.1  lbs.  0:00 


21.5 
20.8 
20.0 

17 .6 


0:45 

1:55 

3:40 

20:10 


^ gm.  platinum  black  ^as  prepared  by  the  method  of  Feulgenl^ 
In  this  method  the  platinum  is  precipitated  by  formaldehyde  anr1  Na  0 ft 
and  the  colloidal  black  caused  to  settle  by  shaking  with  dil.  acetic 
acid.  After  drying  in  a dessicator  over  Eq  304  it  was  shaken  with 
20  gm.  vanillin  in  100  C .0 . alcohol. 

Pressure  Time 
23.6  lbs.  0:00  hrs . 


25.8 
25.4 
25.4 

24.8 


2:00 
20:00 
25:00 
42 : 00 


.2  gm.  platinum  prepared  by  Na  N 0^  fusion  now 

added 


Bottle  warm  from  heat  of  reaction 


22  .7 
18.0 
17 .9 


0:00 
0 : 30 
1:05 


( 1)  Ps&'o  .wan  f iQ9i  | 


!2- 

atalysis  by  Pt  0 

Pt  0 was  prepared  by  the  directions  of  f'&hler ( - )by  boiling 
potassium.  chloroplatmite  w ith  a slight  excess  of  sodium  c ’ hone*  . ■ . 

.06  gnu  K Pt  Cl4  was  dissolved  and  boiled  with  Nag  C 0,^.  Pt  0 was 
precipitated  as  a fine  black  powder,  washed  thoroughly  with  hot  water 
and  dried  over  H2  S 04.  On  shaking  in  hydrogen  with  20  gm.  vanillin 
n 100  C.C.  alcohol,  the  following  results  were  obtained: 

Pressure  Time 
25.7  lbs . 0:00  hrs . 

23.6  8:25 

22.7  23.45 


5 


.0 


.4  gnu  platinum  prepared  by  Na  N O3  fusion  now 
added 


Pressure  drop  required  by  theory  - 5.5  lbs. 


20.5  lbs.  0:00  hrs. 


17 .8 
17 .8 
2 .7 


0: 


: ob 


6:35 


( 2 ) 

Pt  0 was  prepared  after  the  manner  of  Thomsen v ;as  follows: 
1.06  gm.  Ko  Pt  CI4  containing  .5  gm.  platinum  was  dissolved  and  to  it 
was  added  the  calculated  quantity  of  .1  N.  Na  0 H to  precipitate  Pt  0 
on  boiling,  the  Pt  0 was  precipitated  and  washed  by  decantation  until 
free  from  the  neutral  Na  Cl  solution.  It  was  shaken  in  hydrogen  with 
30  gm.  salicylaldehyde  in  100  C.C.  alcohol  with  the  following  results 

(1)  loc . cit. 

(2)  loc.  cit. 


Pressure 
29.5  lbs. 
28.0 

25.7 

.2  gm.  platinum  prepared  by  Na  N O3  fusion  now 

added  3 . 8 

22.7  lbs. 

Required  absorption  (Theoretical)  10.2  lbs.  14.8 

14.8 
7.9 


Time 

0:00  hrs. 
2:15 
17  : 35 


0 : 00  hrs . 
1 : 50 
8:05 


Reduction  o 1 s thyl  methyl  ketone. 

80  gm.  redistilled  ethyl  methyl  ketone  were  shaken  with 
.525  gm.  of  red-brovm  platinum  oxide  from  Na  N O3  fusion  which  had 
been  washed  with  alcohol  and  ether  previous  to  use. 


Pressure 

Time 

Remarks 

45.5  lbs. 

0:00 

37.0 

0 : 15 

Bottle  quite  warm 

32.0 

0:20 

Pressure  increased 

13 . 5 

49.0 

0:20 

15.5 

1:45 

Pressure  increased. 

33.5 

40.0' 

1:45 

33.0 

16:45 

7.0 

• 

53.0  lbs. 

- total  absorpt 

ion  (45  lbs.  - theory) 

Yield  - 74 

gm.  sec.  butyl 

alcohol  - 98°  - 101° 

-24- 


Reduction  of  Phenol. 

62  gin.  redistilled  phenol  was  dissolved  in  50  C .C . alcohol 
and  shaken  with  .65  gin.  ftp 1 at inum  oxide  with  the  following  result 


Pressure 

Time 

Remarks 

31  l"bs. 

0:00  hrs . 

15 

0:40 

Pressure  increased 

16 

47 

0:40 

Bottle  very  warm 

10 

1:50 

Pressure  increased 

37 

50 

1 : 50 

22 

6:30 

Pressure  increased 

28 

40 

6:30 

28.9 

21:10 

11.1 

92.1 

- total  absorption  (Theory  - 

85) 

Small  amount  of  unreduced 

phenol  shaken  out  with  Na  0 H. 

Yield  - 

54  gm.  - 156°  - 7 

0 Gyc  lohexa.no  1 . 

Reduction  of  Benzamid. 

30  gm. 

benzamid  were  dissolved  in  100  c.c.  glacial  acetic 

acid 

and  shaken 

in  hydrogen  with  . 

5 gm.  brown  platinum  oxide. 

Pressure 

Time 

Remarks 

39.3  lbs 

. 0:00  hrs. 

38.6 

0:25 

Catalyst  turned  black. 

35.3 

5:15 

33.8 

18:30 

5.5 

No  product  isolated. 

. 


. 


« 


‘ 

. 


* . 


■ 


. 


-25- 


20  gm.  benzamid  dissolved  in  100  c.c.  warm  alcohol  and  shaken  with 
catalyst  from  above. 


Pressure 

Time 

30.4  lbs. 

0:00  hrs. 

23.4 

3:30 

20.7 

7:30 

18.5 

22 : 30 

18.5 

28 : 00 

Yield  - 9 gm.  hexahydro  benzamid  crystallized  from  alcohol.  Shining 
white  plates  M.P.  185°.  (Lit.  185  - 6°) 

Reduction  of  Kept aldehyde . 

25  gm.  heptaldehyde  dissolved  in  50  c.c.  alcohol  was  shaken  with 
.5  gm.  brown  platinum  catalyst  in  hydrogen. 


Pressure 

30.0  lbs, 

29.0 

Time 

0:00 

1:25 

Remarks 

Catalyst  became  black  instantly 

1.0 

22.4 

0:00 

.5  gm.  more  catalyst  added. 

17.3 

1:30 

16.2 

7 :0G 

16.2 

17:00 

6.2 

1.0 

7.2  total 

aosorpt ion 

(theory  9.3) 

Yield  22  gm.  heptyl 

alcohol  173°' 

- 175° 

-26- 

Palladium 

15  gm.  palladium 

was  dissolved  in  aqua  regia  and  fused  with 

10  gm.  Na  N O3  at  about  550°.  The  precipitated  palladium  was  filterei 

off  and  washed  free  from  nitrates,  the  filtrate  showing  a consider- 

able  quantity  of  unprecipitated 

palladium.  The  catalyst,  which  was 

a dark  reddish  brown  and  showed 

a metallic  glint  in  suspension,  was 

placed  in  the  shaking 

bottle  with  30  gms.  salicyl  aldehyde  and  100. cc 

alcohol . 

Pressure 

Time 

Remarks 

32.0  lbs. 

0:CC 

2S.0 

0:06 

Catalyst  blackened  in  a few 

25.5 

0:16 

seconds.  Gathered  into  flocks 

16.9 

1:10 

which  settle  at  once  on  stopping 

14.6  1:53 

17.4  total  absorption. 

shaker , 

(Theory  for  saligenin  - 10.2) 

No  saligenin  could  be 

isclat  ed 

from  the  reduction  product,  but  14  gm. 

ortho  cresol  was  obtained,  185° 

- 187°  which  could  be  easily  crystal- 

lized.  A high  boiling,  syrupy 

residue  remained,  probably  a con- 

densation  product. 

A second  run  was  made 

using  the 

same  catalyst. 

Pressure 

Time  ' 

Remarks 

29.0 

0:00 

27.8 

0:18 

Shaken  with  air  18  min. 

1.3 

26.0 

0:00 

21.1 

1:22 

18.4 

2:39 

13.3 

17:17 

■ 


-37- 


13.7 

14.0  - total  absorption.  Yield  - S gm.  pure  o cresol. 

In  these  experiments  .2115  gm.  palladium  was  used. 

The  brown  palladium  oxide  showed  the  same  chemical  properties  as 
that  of  platinum,  partial  solubility  in  aqua,  regia  but  soluble  in 
H Br  only  on  warming. 

Iridium 

J gm.  of  insoluble  material  obtained  from  platinum  scrap  assumed  to  be 
iridium  was  shaken  with  25  gm.  cinnamic  acid  dissolved  in  100  c.c. 
alcohol.  10  lbs.  of  hydrogen  was  absorbed  in  2 hrs.  and  20  min,  A 
mixture  of  liquids  was  obtained  and  a small  amount  of  aihydro  cinna- 
mic acid  was  isolated  M.P.  48.5  (Lit.  - 48.7) 


* 


CONCLUSION 


-28- 


The  results  of  the  experiments  tabulated  fcsre  seem  to  indicate 
that  the  brown  amorphous  powder  obtained  when  Ft  CI4  is  fused  with 
Na  N 0^,  is  an  oxide  of  platinum  having  a higher  oxygen  content  than 

Pt  oa. 

Its  catalytic  activity  is  apparently  due  to  a lower  oxide  which 
is  formed  in  the  reduction  bottle,  (probably  Pt  0 ) . Its  superior 
activity  to  Pt  0 is  likely  due  to  physical  form  (state  of  division), 
and  its  superiority  over  platinum  black  is  probably  due  to  a larger 
oxide  content  and  to  a gradual  reduction  of  the  higher  oxide  to  the 
active  form  which  sustains  the  catalysis. 

Its  ease  of  preparation  and  convenient  application  should 
commend  its  use  in  place  of  platinum  black,  the  preparation  of  which 
is  quite  difficult  if  an  active  form  is  to  be  obtained. 




